#!/usr/bin/env node

// 定义 Circle 类  
class Circle {  
    constructor(radius) {  
        this.radius = radius;  
    }  
    get diameter() {  
        return 2 * this.radius;  
    }  
    get area() {  
        return Math.PI * this.radius * this.radius ;  
    }   
    get circumference() {  
        return 2 * Math.PI * this.radius;  
    }  
}  

module.exports = Circle;